1. Field of the Invention
The present invention relates to a mixer for homogenizing a mixture of products at least one of which is present in the liquid phase.
2. Description of the Prior Art
The mixer herein is especially, but not exclusively, adapted for use in the preparation of paints for motor vehicles. For such application, the mixer is basically intended to be used for the resuspension and storage of base paints used on automobile bodies, corresponding to the various vehicles in manufacture.
In practice, it is essential that these base paints be perfectly homogeneous in order that the quantities set aside in accordance with the preparative formulas correspond to perfectly uniform pigment quantities, an essential condition for assuring faithful color reproduction.
Usually, the mixer is driven in rotation by a mechanical device whose shaft passes through a lid integrally fixed upon the base paint container.
It is known at the present time that there exists on the market several types of mixers of this kind, of which the most common essentially comprise:
either a sheet-metal flap furnished with shutters which rotates about the rotating shaft while forming a vertical plane moving in the liquid, a part of the paint passing through shutters and resulting in a certain degree of mixing; PA1 or a lower helical primary blade but with a very steep pitch, and a secondary, flat, blade situated near the surface of the liquid, this mixer causing during its rotation, a mixing of a different nature from that of the previously described type, which produces a vertical convection movement; PA1 or else a helical blade whose pitch is shallower than in the preceding case, and which provides similarly effective mixing with, however, a vortex capable of creating an air-paint and emulsion mixture being formed at the center of the device.
These three types of mixers are commonly used without it having been possible to clearly demonstrate an incontestable superiority of one compared to the others, principally during laboratory tests and under conditions simulating the viscosity of the paint.
On the other hand, these mixers present a serious drawback during the mixing of base paints in which there is considerable settling of suspended material, for example, in the case of metallized bases in which there exists a deposit of several centimeters of concentrated aluminum powder. In practice, none of these mixers have shown themselves to be sufficiently effective, the operator being forced to carry out manual mixing before working with the mixing machine.